1. Field of the Invention
The invention relates to the field of containers for providing liquid concentrates for making ready-to-use dialysis fluid for a dialysis treatment of a patient by an artificial kidney.
2. Description of the Related Art
In case of kidney failure the functions of the human kidneys have to be substituted by an artificial kidney device. Wide spread therapies comprise peritoneal dialysis and hemodialysis. In peritoneal dialysis, dialysis fluid is conducted via special implanted catheters to the peritoneal cavity of a patient and regularly exchanged with fresh fluid, thus purifying the human blood by diffusion of substances to be removed and by extracting excess water by osmotic pressure gradients through the peritoneum of the patient.
In hemodialysis the blood of a patient is circulated in an extracorporeal blood circuit for several hours. The blood passes the blood chamber of a dialyser where a semipermeable membrane, most commonly in the shape of thousands of hollow fibres, separates a blood chamber from a dialysate chamber that is part of a dialysate circuit. The blood is purified from substances to be removed by diffusion through the membrane as such substances are usually not contained in the dialysate flowing into the dialysate chamber. Other substances that are to be retained in the blood at least in certain concentrations and that can also pass the membranes like electrolytes are contained in the fresh dialysate in physiological concentrations. By applying a pressure gradient excess water can be transferred from the blood to the dialysate chamber and then be removed together with the dialysate exciting the dialysate chamber.
Most contemporary hemodialysis devices prepare the dialysate required for the hemodialysis treatment during the treatment from concentrates and water in a single-pass system, i.e. the prepared dialysate only passes the dialyser once and is discarded thereafter. Depending on the type of dialysate to be used one or two concentrates are required. In the case of bicarbonate dialysis that currently represents the most common dialysis mode two concentrates are necessary because of chemical incompatibilities of some of the substances. The first or “A”-component usually consists of an acidic part that also contains most of the required electrolytes. The second or “B”-component consists mainly of sodium bicarbonate in this case. Whereas the second component can also be delivered in dry powder form, the first component is still widely distributed as a fluid in rigid containers if no central concentrate supply system exists where the concentrate is prepared at a central location and then distributed to the treatment places via a piping network.
Typical dilution ratios of the A-component with water are about 1+33, 1+34 or 1+44, the B-component contributing further shares between 1 to 2 parts of liquid. Common dialysate flow rates for a hemodialysis treatment are of the order of 500 ml/min. Taking a four hour treatment a liquid volume of about 120 liters has to be circulated through the dialysate chamber requiring concentrate volumes of at least 3 to 4 liters each. To enable a variation of concentration ratios and also to provide a certain tolerance to prolong a treatment and to compensate the waste of dialysate in certain conditions of a hemodialysis device when for security reasons the continuously prepared dialysate is short-circuited to the drain, usual containers for liquid dialysate concentrates contain 5 or more liters of liquid concentrate.
The dialysate prepared by diluting the concentrates with water on-line during a treatment of a patient may also be used as substitution liquid in the case of a hemofiltration or hemodiafiltration treatment. Today many treatment devices also provide for such on-line substitution modes leading to an even higher demand of liquid concentrates.
Up to now the fluid concentrates have usually been delivered in rigid plastic containers as the weight of the concentrate requires a certain stability of the container. Such containers also simplify the shipping of large lots as they can easily be arranged in layers on top of each other.
These rigid containers have the disadvantage that because of their rigidity they are comparatively expensive as the container walls have to be thick enough leading to higher material expenses. Furthermore, the empty containers are bulky making the further processing cumbersome. The large amount of material to be recycled or discarded adds further to the cost.